1. Field of the Invention
The present invention relates generally to an automatic transmission suited for use in an automotive vehicle and more specifically to such a type of transmission wherein N - D select shock is attenuated.
2. Description of the Prior Art
A four foward speed type automotive automatic transmission of the type disclosed in NISSAN AUTOMATIC TRANSMISSION SERVICE MANUAL published in Feb. 1984, includes a low clutch and a fixed one-way orifice arrangement which is fluidly interposed between a source of line pressure and the servo chamber of the clutch. This one-way orifice is arranged to restrict the flow of hydraulic fluid to the clutch and allow the fluid to drain rapidly therefrom.
The system further includes an accumulator which is operatively connected with the clutch in a manner to modify the rate at which hydraulic pressure develops in the clutch servo chamber and smooth the engagement characteristics of the clutch during shifting.
When this type of transmission is shifted from neutral (N) to drive (D) range, a notable N-D select shock tends to be produced. To overcome this it is possible to reduce the size of the fixed orifice and increase the flow resistance provided thereby. However, this causes the charging time of the accumulator to become excessively long and leads to an unacceptably increased N-D time lag.